BeanPropertyComparator.java

/*
 * Copyright 2011-2012 Blazebit
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.blazebit.blazefaces.model;

import java.util.Comparator;
import java.util.logging.Logger;

import javax.el.MethodExpression;
import javax.el.ValueExpression;
import javax.faces.context.FacesContext;

/**
 * Generic comparator for column sorting.
 */
public class BeanPropertyComparator implements Comparator {

	private ValueExpression sortBy;
	
	private boolean asc;
	
	private String var;
	
	private MethodExpression sortFunction;
	
	private final static Logger logger = Logger.getLogger(BeanPropertyComparator.class.getName());
	
	public BeanPropertyComparator(ValueExpression sortBy, String var, SortOrder sortOrder, MethodExpression sortFunction) {
		this.sortBy = sortBy;
		this.var = var;
		this.asc = sortOrder.equals(SortOrder.ASCENDING);
		this.sortFunction = sortFunction;
	}

	@SuppressWarnings("unchecked")
	public int compare(Object obj1, Object obj2) {
		try {
			FacesContext context = FacesContext.getCurrentInstance();
			
			context.getExternalContext().getRequestMap().put(var, obj1);
			Object value1 = sortBy.getValue(context.getELContext());
			context.getExternalContext().getRequestMap().put(var, obj2);
			Object value2 = sortBy.getValue(context.getELContext());
			
			//Empty check
			if(value1 == null)
				return 1;
			else if(value2 == null)
				return -1;
				
			int result;
			if(sortFunction == null) {
				result = ((Comparable) value1).compareTo(value2);
			} else {
				result = (Integer) sortFunction.invoke(context.getELContext(), new Object[]{value1, value2});
			}
			
			return asc ? result : -1 * result;
			
		} catch (Exception e) {
			logger.severe("Error in sorting");
			
			throw new RuntimeException(e);
		}
	}
}